42

and mashed. Those zones, extending for a few score yards, alternate with broader areas in which the folding has not been so severe, and the rocks lie regularly disposed for considerable distances. In the tightly folded zones the mashing and twisting of the beds has been extreme, though faulting, apart from minor slips, is rare. The closeness of the folds, and the sharpness of the turns in them, with the absence of extensive faulting indicates that these rocks were folded under such pressures that they were sensibly plastic. The. recurrent zones of severe contortions, separated by less disturbed areas, were caused by the moun-

Scale of feet S /O /.

Geo/o g1ca/ Survey, Canada.

Figure 2. Sketch of low cliff of argillites in the Maude formation on King creek, illustrating typical manner of folding in these rocks. Note parallel folding and carinate anticline.

tain-building stresses having been periodically relieved by failure of the beds in these zones. The types of folds into which the rocks are bent, and typical minor faulting are well shown in Figures 2, 3, and 4 and Plate XIB.

The rocks are extremely jointed, most joints being normal to the bedding, and many containing films of black, tarry matter, which also occurs along bedding surfaces, and in irregular veins of coarsely crystalline yellowish calcite cutting the argillites.

The thickness of the formation is unknown, as the base has not been seen. Dawson! describes very similar rocks as occur-

1 Dawson, G. M., Geol. Surv., Can., Rept. of Prog., 1878-79, p. S5B.